1. Field of the Invention
The present invention relates to an information transmitting device and method, an information terminal device and an information terminal receiving method, a digital broadcast receiving device and method, and an output time calculating device and method which are suitably used for a system for delivering data on contents by utilizing an empty band of a transponder which is caused by the completion of an ordinary digital BS (Broadcast Satellite) broadcast, for example.
2. Description of the Related Art
In the digital BS broadcast, programs including digital video data, digital audio data and other information have been broadcast by using MPEG (Moving Picture Coding Experts Group) 2-TS (Transport Stream). In the MPEG2-TS, programs for a plurality of channels can be multiplexed into one carrier and can be transmitted. For example, eight transponders having a transmission band of 30 Mbps are mounted on an artificial satellite (BS-4 succeeding artificial satellite) carrying out the digital BS broadcast. One transponder can transmit six channels in an SDTV (Standard Definition Television) broadcast and two channels in an HDTV (High Definition Television) broadcast.
In some of ordinary programs broadcast in the digital BS broadcast, the time zone for broadcasting is restricted to the day. For this reason, when the ordinary broadcast is completed at night, an empty band is generated in the transponder. Therefore, there has been proposed that data on contents are delivered by effectively utilizing the empty band of the transponder which is generated after the completion of the broadcast.
In other words, the data on the contents are transmitted from a broadcasting station to a receiver of each home through the BS artificial satellite by utilizing the empty band of the transponder which is generated after the completion of the ordinary broadcast at night. The data on the contents are received by the receiver of each home. The receiver of each home comprises a storage device such as a hard disk drive. The data on the contents thus received are once stored in the storage device. The data on the contents stored in the storage device can be reproduced later by a user. When the data on the contents stored in the storage device are reproduced, the data on the contents are read from the storage device of a receiving terminal of each home and an image thereof is projected onto a television receiver of each home.
Such a delivery service for the data on the contents utilizes the empty band generated by the completion of the ordinary broadcast. Therefore, there is an advantage that the data on the contents can be delivered at a low cost. There can be proposed various data on the contents to be delivered, for example, video data such as a movie or a drama. Such a delivery service for the data on the contents can also be utilized as a delivery service for a video on demand or a music.
Such a delivery service for the data on the contents utilizes the empty band of the transponder after the completion of the ordinary program broadcast, thereby transferring the data. Therefore, a time zone in which the data on the contents can be delivered is restricted depending on a time required for the ordinary program broadcast. Moreover, a band which can be maintained for transmitting the data on the contents is limited to the empty band of the transponder while the ordinary broadcast is completed. For this reason, it is considered that the data on the contents cannot be delivered within a time in which the empty band is generated in the transponder after the completion of the ordinary broadcast or a sufficient band cannot be maintained to deliver the data on the contents in the empty band of the transponder.
In such a delivery service for the data on the contents, it has been proposed that the data are transmitted at a higher speed than a real time in order to shorten a time required for delivering the data on the contents or the data are transmitted at a lower speed than the real time in order to maintain a sufficient band to transmit the data on the contents.
More specifically, it is supposed that a time zone in which the ordinary broadcast is not carried out takes four hours, for example, from one o'clock at night to five o'clock in the morning. In this case, if a time required for delivering the data on the contents is four hours or less, it is possible to transmit the data on the contents in a real time for four hours from one o'clock at night to five o'clock in the morning in which the ordinary broadcast is completed.
However, in the case in which the time required for delivering the data on the contents is eight hours in a real time, for example, the data on the contents cannot be delivered completely for four hours from one o'clock at night to five o'clock in the morning in which the ordinary broadcast is completed.
Thus, in the case in which the time required for transferring the data on the contents cannot be maintained sufficiently, the data on the contents are transferred at a speed which is a double of the real time, for example. When the data on the contents are transmitted at the speed which is a double of the real time, for example, the data on the contents which are transferred for eight hours in the real time, for example, can be transmitted in four hours. Accordingly, even if the time required for delivering the data on the contents is eight hours in the real time, for example, a transfer speed is doubled so that the data on the contents can be completely delivered for four hours from one o'clock at night to five o'clock in the morning in which the ordinary broadcast is completed.
As described above, moreover, eight transponders having a transmission band of 30 Mbps are mounted on the digital BS artificial satellite and one transponder can transmit six channels in the SDTV broadcast and two channels in the HDTV broadcast. For example, it is assumed that the data on the contents are delivered by utilizing a time at which a program for the SDTV broadcast is ended. In this case, if the data on the contents for the SDTV equivalent to the program which has been broadcast are to be delivered, the data on the contents can be exactly transferred in a real time by utilizing an empty band. However, if the data on the contents of the HDTV are to be delivered, a sufficient empty band is not generated on the transponder through the completion of the program which has been broadcast for the SDTV so that the data on the contents cannot be transferred.
Thus, in the case in which a sufficient band for transferring the data on the contents cannot be maintained, the data on the contents are transferred at a lower speed than the real time. For example, if the transfer speed of the data on the contents of the HDTV for one hour in the real time is reduced to a quarter and the same data are transferred, the transmission band is reduced to a quarter. Consequently, the data on the contents for the HDTV can be transferred in the empty band of the transponder which is generated by the completion of the program which has been broadcast for the SDTV.
For example, moreover, it is assumed that data on two contents for the SDTV are to be delivered by utilizing the ending time of a program which is being broadcast for the SDTV. If the data on the contents are to be delivered in the real time, it is impossible to simultaneously deliver the data on two contents by utilizing an empty band generated by the completion of the program which is being broadcast for one SDTV.
In this case, a transfer speed for information about the contents is reduced to a half. When the transfer speed is reduced to a half, a transmission band is reduced to a half. Consequently, the data on contents for two SDTVs can be transferred at the same time by utilizing the empty band of the transponder which is generated by the completion of the program which is being broadcast for one of the SDTVs.
For example, furthermore, it is assumed that an empty band of the transponder for 10 Mbps is maintained. On the other hand, it is assumed that the data on the contents to be transmitted have a band of 8 Mbps. In this case, a null packet is usually inserted for the transmission. Consequently, a band of 2 Mbps is wasted. If the transfer speed of the data on the contents can be changed, the data can be transferred without causing such a waste.
In such a system that the data on the contents are to be transferred by utilizing the empty band of the transponder while a broadcast is completed and an empty band is generated in a transponder at night, thus, the data on the contents for a long time can be transferred in a limited time through data transmission at a higher speed than a real time. Moreover, the data on the contents in a wide band can be transferred in a limited transmission band or data on a plurality of contents can be transferred at the same time through data transmission at a lower speed than the real time.
However, when the data are transferred at a different speed from the real time, time information is lost so that a time base cannot be restored. For this reason, there is a problem in that a time cannot be set on the basis of a PCR (Program Clock Reference) sent in a TS packet to reproduce a program.